Tagnin, Laura,Ní Ríordáin, Máire,The growing population of students that are learning science through a Content and Language Integrated Learning approach (CLIL) has led to concerns about these students’ ability to fully participate in a rich classroom discourse to develop content knowledge. A lack of information about science development through classroom discourse in CLIL settings brought us to focus on the questions teachers ask in upper secondary CLIL biology classrooms. Our aim was to understand how these questions effect science content learning opportunities. A multiple-case study design was implemented to examine and understand the complexities of teacher-student interactions. Data were collected in three case studies, each located in a different school (two in Germany and one in Italy), where CLIL senior secondary science classrooms were observed and audio-recorded. Classroom talk transcripts were analyzed using a mixed methods approach to discourse analysis.